Neither, they aren't regular enough.We are normalizing vector <u, v, 1 + (0.5/(√2 - 1) - 1)∙(1 - u²)∙(1 - v²)>, where u,v are face coordinates in -1..1. This gives pretty homogenous spacing, but the inverse has to be found by Newton solver. Luckily, it's only rarely used in practice, so it's not a problem.